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Saturday night under Mendip

PeteHall

Moderator
During maintenance work at a potable watet borehole in Shepton Mallet, a scaffolder dropped his impact driver into the water. There were concerns that the lithium ion battery could pollute the water supply and after unsuccessful attempts at magnet fishing, they got in touch with some local cavers they knew.

A message went out on a Mendip cavers Facebook group and the next day, Kev and I were looking down a 50m hole, ready for an unusual evening underground.

We'd brought SRT and diving kit, but they had managed to pump the well down to a depth of 1.6m, so it seemed diving kit would be redundant.

We sent a gas meter down first, then I  put on my long-john wetsuit (opting to leave the jacket off) and headed down on SRT, with a hood and mask in my bag, just in case.

On reaching the water surface it became clear that 1.6m was the depth above the pumps,  not the depth to the bottom... I plumbed it with a piece of lead on the end of my SRT rope and estimated a further 10m to the bottom, leaving me little choice but to return up the 50m back to surface and reorder my equipment for diving.

Meanwhile, Kev set about magnet fishing from just above the water, but only managed to retrieve a length of scaff tube...

Once I was kitted up, Kev returned half way up, to take a break in a side passage that had been dug unsuccessfully looking for water, while I descended alongside my diving cylinders that were cautiously lowered from the top. Once I was past him, Kev followed me down and helped me kit up in the water, observing that the magnet fishing had had a slightly detrimental effect on the previously crystal clear water.

After a bit of faff, I was off the rope, in the water. Redundant SRT items removed and slack rope tied out of the way above water. Diving kit on, tested and ready to descend.

Below the pumps, the viz immediately returned and the drill could be seen right next to the lead weight on bottom of my line, nestled in a cradle of rusty steel beams. No wonder the magnet hadn't managed to find it!

With the drill returned to a tackle bag above water, I made a second descent to have a look at two side Passages that I'd spotted, one at the base of the shaft and  one about 4m below the waterline. Both were about 5-6m long blasted tunnels, that had been dug looking for water. The lower tunnel had clearly succeeded, as by the time I'd returned to dive base, my tackled bags were hanging underwater and Kev, who'd been several metres above the water had just got a welly full!

We joked about getting the beers sent down and waiting for the water to carry us back out, but agreed Kev would get a  bit cold in a fury suit, so it was best to use the SRT rope instead.

With Kev part way up to steer it, the chaps at the top hauled out the bag of diving kit and we were soon back at the surface, de-rigging.

Mission accomplished.

We both had plenty of fun and the scaffolder was clearly very relieved and has pledged a donation to Mendip Cave Rescue in return for our efforts. A good result all around.  (y)
 

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Mark Wright

Member
cavemanmike said:
Thought the scaffolder would have had his impact driver on a lanyard but that would have spoilt all your fun  :clap: :clap:

It's quite rare to see 'scaffolder' and 'lanyard' in the same sentence.

Mark
 

Pitlamp

Well-known member
Nice one - and great PR for the caving community.

Out of interest it looked like there was quite a flow; was that just water movement from ascending bubbles or it it actually flowing up at surface? It seemed to clear quickly.
 

PeteHall

Moderator
It was a bit murky when I was kitting up, from the earlier magnet fishing, but was crystal clear by the time I got a few metres down, as it was clearing/ filling from the bottom.

They switched the pumps off once I was ready to dive and from that time to when I was de-kitting again (15 minutes tops) the water had risen about 2m, so in round numbers, at 2m diameter at the bottom, that would be about 25 cubes per hour refill rate.
 

PeteHall

Moderator
PeteHall said:
so in round numbers, at 2m diameter at the bottom, that would be about 25 cubes per hour refill rate.

Not far off. BGS records show a yield of 5,000 gallons per hour when it was dug, which would be about 23 cubes.
 

Duncan Price

Active member
This is the second dive at this site:

December 2004
Diver: J Beal

The diver had been asked to dive in a well... ...where a gas monitor and a large torch had been dropped into the water and needed recovering. Diver and support abseiled 55 m down the 2 m diameter shaft between two water pipes to access the adit at the water level. Diver then kitted up to enter the water with pony cylinders and no fins to squeeze between the pumps to a depth of only 6m to recover the items. Initial visibility was excellent allowing another adit to be seen. This was half-full with silt but was followed for 10 m to a 90 degree bend where a blasted face was found. A slow prussik out introduced the diver to the joys of double ropes and shunts.
 

Mark Wright

Member
Back in the early 80?s the TSG did a similar exercise for a mining company in Derbyshire. I can?t remember the name of it but it was on the right between Calver and Bakewell at the Calver end of the road.

Chris Rhodes and I descended a similar sized shaft to recover a load of wriggly tin that had been thrown down the water pumping shaft and damaged the pumping hoses.

In return the mining company gave us access to explore another more interesting shaft on their land.

It was a great day out and everybody was happy with the outcome.

That, however, was in the 80?s when Health and Safety legislation was not what it is today.

The number of Health and Safety laws that have been broken on this occasion by the company who put out the call on Facebook are considerable and if the HSE got wind of it, heads would certainly roll. The fines could likely run into the 10?s if not 100?s of thousands of ??s!!!

Whilst, as Pitlamp says, it might be good PR for the caving community I?d be more inclined to accept the donation and pull this thread from the forum before it is spotted by the powers that be.

Mark


 

Pitlamp

Well-known member
Mark - was that ever recorded anywhere? I ask because there's a Peak District sump index in the pipeline and it'd be useful to have at least a note of it in there. Could you send a PM rather than posting here, in case your advice immediately above is taken?
 

PeteHall

Moderator
Mark Wright said:
The number of Health and Safety laws that have been broken on this occasion by the company who put out the call on Facebook are considerable and if the HSE got wind of it, heads would certainly roll. The fines could likely run into the 10?s if not 100?s of thousands of ??s!!!

Whilst, as Pitlamp says, it might be good PR for the caving community I?d be more inclined to accept the donation and pull this thread from the forum before it is spotted by the powers that be.

Mark

For the record, the company did not put a call on Facebook. An employee contacted friends who were cavers, those cavers put a call on a private cavers Facebook group.

I have removed details above that could identify the location of the site.
 

mikem

Well-known member
The company will still be fairly easy to identify if it sparks an investigation, so I'd follow Mark's advice.
 

mrodoc

Well-known member
You are safe anyway as you didn't take any money. Otherwise it would have been a commercial dive. Estelle (BEC) and I have received payment in kind in the past but indirectly (freeing a prop once and what turned out to be a rather nefarious activity in Portland Harbour with Mrs Mrodoc).
 

Cantclimbtom

Active member
At about 50 secs in the vid I see 2 knots on that dark rope and a big gap to something maybe a shunt just above water surface, at 1:30 in vid there is much less rope below the 2nd knit and shunt or whatever it was is submerged, at 3:00 or so water is now near the second knot. That water is rising up that bore very quickly!
 

PeteHall

Moderator
Yes, they switched the pumps off before I dived. By the time I was back in my SRT kit afterwards, it had come up a couple metres.

The video isn't continuous, so it's not as quick as it looks though...
 

PeteHall

Moderator
We returned with Chunky and his camera, plus a GoPro from one of the chaps on site.

Since Frampton's have put the underwater GoPro footage on YouTube, I see no reason not to share it here.

https://youtu.be/2cjTffPZjF4

Note the air-bell in the side passage, where the water enters the well. This is perched at a reasonable depth below the water surface in the well (over 8m while we were there,  but obviously varies depending on pumping).

My theory is that as the water enters the well, the pressure drops from circa 30m depth (un-pumped water level) to circa 8m depth.  The sudden drop in pressure causes dissolved air to come out of solution, forming a perched air-bell. Any scientists out there care to verify of quash this theory?

Video credit to Chunky, with support from: J Burkey, L Phelps, D Price, T Williams and me.
 
Managed to recover some scaff poles, spanner & rubbish.



 

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